Lazy eye (amblyopia) [20166981]

Lazy eye (amblyopia) is reduced vision in one eye caused by abnormal visual development early in life. The weaker — or lazy — eye often wanders inward or outward.

Amblyopia generally develops from birth up to age 7 years. It is the leading cause of decreased vision in one eye among children. Rarely, lazy eye affects both eyes.

Early diagnosis and treatment can help prevent long-term problems with your child's vision. Lazy eye can usually be corrected with glasses or contact lenses, or eye patches. Sometimes surgery is required.

When to see a doctor

See your child's doctor if you notice his or her eye wandering at any time after the first few weeks of life. A vision check is especially important if there's a family history of crossed eyes, childhood cataracts or other eye conditions.

For all children, a complete eye exam is recommended between ages 3 and 5.

Lazy eye develops because of abnormal visual experience early in life that changes the nerve pathways between a thin layer of tissue (retina) at the back of the eye and the brain. The weaker eye receives fewer visual signals. Eventually, the ability of the eyes to work together decreases, and the brain suppresses or ignores input from the weaker eye.

Anything that blurs a child's vision or causes the eyes to cross or turn out may result in lazy eye. Common causes of the condition include:

Muscle imbalance (strabismus). The most common cause of lazy eye is an imbalance in the muscles that position the eyes. This imbalance can cause the eyes to cross in or turn out, and prevents them from tracking together in a coordinated way.

Difference in sharpness of vision between the eyes (refractive anisometropia). A significant difference between the prescriptions in each eye — often due to farsightedness but sometimes to nearsightedness or an imperfection on the surface of the eye called astigmatism — can result in lazy eye. Glasses or contact lenses are typically used to correct these refractive problems. In some children lazy eye is caused by a combination of strabismus and refractive problems.

Deprivation. Any problem with one eye — such as a cloudy area in the lens (cataract) — can deprive a child of clear vision in that eye. Deprivation amblyopia in infancy requires urgent treatment to prevent permanent vision loss. Deprivation amblyopia often results in the most severe amblyopia.

Your doctor will conduct a thorough eye exam, checking for eye health, a wandering eye, a difference in vision between the eyes or poor vision in both eyes. Eyedrops are generally used to dilate the eyes. The eyedrops cause blurred vision that lasts for several hours or a day.

The method used to test vision depends on your child's age and stage of development:

Preverbal children. A lighted magnifying device can be used to detect cataracts. Other tests can assess an infant or toddler's ability to fixate his or her gaze and to follow a moving object.

Children ages 3 and older. Tests using pictures or letters can assess the child's vision. Each eye is patched in turn to test the other.

It's important to start treatment for lazy eye as soon as possible in childhood, when the complicated connections between the eye and the brain are forming. The best results occur when treatment starts before age 7, although half of children between the ages of 7 and 17 respond to treatment.

Treatment options depend on the cause of lazy eye and on how much the condition is affecting your child's vision. Your doctor might recommend:

Corrective eyewear. Glasses or contact lenses can correct problems such as nearsightedness, farsightedness or astigmatism that result in lazy eye.

Eye patches. To stimulate the weaker eye, your child may wear an eye patch over the stronger eye. The patch is generally worn for two to six hours a day.

Bangerter filter. This special filter is placed on the eyeglass lens of the stronger eye. The filter blurs the stronger eye and, like an eye patch, works to stimulate the weaker eye.

Eyedrops. A twice-weekly eyedrop of a medication called atropine (Isopto Atropine) can temporarily blur vision in the stronger eye. This will encourage your child to use the weaker eye, and offers an alternative to wearing a patch. Side effects include sensitivity to light.

Surgery. If your child's eyes cross or wander apart, your doctor may recommend surgical repair for the eye muscles. Your child may also need surgery if he or she has droopy eyelids or cataracts.

Activity-based treatments — such as drawing, doing puzzles or playing computer games — are now available. The effectiveness of adding these activities to other therapies hasn't been proved.

For most children with lazy eye, proper treatment improves vision within weeks to several months. Treatment might last from six months to two years.

It's important for your child to be monitored for recurrence of lazy eye — which can happen in up to 25 percent of children with the condition. If lazy eye recurs, treatment will need to start again.